Tool, tool holder, method of driving the same, machine tool, and tool management system

ABSTRACT

A tool, attachable to a spindle of a machine tool and capable of changing independently a rotational speed of a cutting tool from that of the spindle, provided with a cutting tool for machining a workpiece, an electric motor for driving the machining tool, a generator for generating electric power to drive the electric motor by the rotation of the spindle, a tool holding part for rotatably holding the cutting tool, a casing for holding the electric motor, the generator, the tool attachment part, and the tool holding part, and a locking part for preventing rotation of the casing by engagement with a non-rotating part of the machine tool.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a tool and a tool holder to beused in a machine tool. More particularly, the present invention relatesto a tool and tool holder removably attachable to the spindle of amachine tool.

[0003] 2. Description of the Related Art

[0004] In a machine tool provided with a spindle such as machiningcenter, the maximum rotational speed of the spindle is determined by thestructure of a bearing rotatably supporting the spindle and alubrication system of this bearing. For this reason, when it isnecessary to rotate a tool at a higher rotational speed than the maximumrotational speed of the spindle, an accelerating apparatus is used.

[0005] As the accelerating apparatus, for example, an acceleratingapparatus provided with a gear mechanism such as an epicyclic gearingwhich holds the tool and is removably attachable to the spindle is wellknown.

[0006] However, when raising the rotational speed of the tool to ahigher speed than the maximum rotational speed of the spindle by theabove gear mechanism, the accelerating apparatus increasingly generatesheat at a super high rotational speed such as tens of thousands tohundreds of thousands of revolutions per minute, so the machiningtolerance of a workpiece can be influenced by the heat. Further, at theabove super high rotational speed, the noise from the acceleratingapparatus can also increase. Furthermore, a highly reliable precisionstructure able to withstand the above super high rotational speed isrequired for the accelerating apparatus, so there is the disadvantagethat the manufacturing cost becomes relatively high.

SUMMARY OF THE INVENTION

[0007] An object of the present invention is to provide a tool and atool holder capable of changing the rotational speed of a machining toolfor machining a workpiece independently from the rotational speed of aspindle of a machine tool.

[0008] Another object of the present invention is to provide a machinetool provided with the above tool and tool holder.

[0009] Still another object of the present invention is to provide amethod of driving the above tool.

[0010] Still another object of the present invention is to provide atool management system for managing the above tool.

[0011] According to a first aspect of the present invention, there isprovided a tool attachable to a spindle of a machine tool comprising amachining tool for machining a workpiece; an electric motor for drivingthe machining tool; and a generator for generating electric power todrive the electric motor by the rotation of the spindle.

[0012] According to a second aspect of the present invention, there isprovided a tool attachable to a spindle of a machine tool comprising amachining tool for machining a workpiece; an electric motor for drivingthe machining tool; a generator for generating electric power to drivethe electric motor by the rotation of the spindle; and a control meansfor controlling a supply of electric power generated by the generator todrive and control the machining tool.

[0013] According to a third aspect of the present invention, there isprovided a tool attachable to a spindle of a machine tool comprising amachining tool for machining a workpiece; an electric motor for drivingthe machining tool; a generator for generating electric power to drivethe electric motor by the rotation of the spindle; an electric powerreceiving part other than the electric motor for receiving supply of theelectric power; a secondary battery able to supply power to the electricpower receiving part; and a charging circuit for charging the secondarybattery with part of the electric power generated by the generator.

[0014] According to a fourth aspect of the present invention, there isprovided a tool attachable to a spindle of a machine tool comprising amachining tool for machining a workpiece; an electric motor for drivingthe machining tool; a generator for generating electric power to drivethe electric motor by the rotation of the spindle; a processing circuitfor processing data related to machining of the workpiece by themachining tool; and a transmitting and receiving circuit for performingat least one of transmission and reception of a wireless signalindicating information related to machining of a workpiece by themachining tool.

[0015] According to a fifth aspect of the present invention, there isprovided a tool holder attachable to a spindle of a machine tool forrotatably holding a machining tool for machining a workpiece, the toolholder comprising an electric motor for driving the machining tool and agenerator for generating electric power to drive the electric motor bythe rotation of the spindle.

[0016] According to a sixth aspect of the present invention, there isprovided a machine tool comprising a machine tool body provided with aspindle, a driving means for driving the spindle, and at least onecontrol axis for changing a relative position between the spindle and aworkpiece; a control apparatus for controlling the driving means and thecontrol axis in accordance with a machining program; and a toolattachable to the spindle and provided with a machining tool formachining a workpiece, an electric motor for driving the machining tool,and a generator for generating electric power to drive the electricmotor by the rotation of the spindle.

[0017] According to a seventh aspect of the present invention, there isprovided a method of driving a tool attachable to a spindle of a machinetool, the tool being provided with a machining tool for machining aworkpiece, an electric motor for driving the machining tool, and agenerator for generating electric power to drive the electric motor bythe rotation of the spindle, comprising the steps of generatingalternating current having a frequency in accordance with the rotationalspeed of the spindle; driving the electric motor by the generatedalternating current; and controlling the rotational speed of themachining tool in accordance with the frequency of the alternatingcurrent.

[0018] According to an eighth aspect of the present invention, there isprovided a tool management system comprising a tool attachable to aspindle of a machine tool, the tool comprising a machining tool formachining a workpiece, an electric motor for driving the machining tool,a generator for generating electric power to drive the electric motor bythe rotation of the spindle, a processing circuit for processing datarelated to machining of the workpiece by the machining tool; atransmitting and receiving circuit for performing at least one oftransmission and reception of a wireless signal indicating informationrelated to machining of a workpiece by the machining tool; and amanagement apparatus for performing at least one of reception of datafrom the transmitting and receiving circuit and transmission of data tothe receiving circuit and managing the data.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] These and other objects and features of the present inventionwill be more apparent from the following description of the preferredembodiments given in relation to the accompanying drawings, wherein:

[0020]FIG. 1 is a view of the configuration of a machining center as anexample of a machine tool according to the present invention;

[0021]FIG. 2 is a sectional view of a tool according to the firstembodiment of the present invention;

[0022]FIG. 3 is a view of the connection state of a motor and generator;

[0023]FIG. 4 is a view of the configuration of an electrical system of atool according to a second embodiment of the present invention;

[0024]FIG. 5 is a view of the configuration of an electrical system of atool according to a third embodiment of the present invention;

[0025]FIG. 6 is a view of the configuration of an electrical system of atool according to a fourth embodiment of the present invention;

[0026]FIG. 7 is a view of the configuration of an electrical system of atool according to a fifth embodiment of the present invention;

[0027]FIG. 8 is a sectional view of a tool according to a sixthembodiment of the present invention;

[0028]FIG. 9 is a view of the configuration of an electrical system of atool and the configuration of a tool management system using the sameaccording to the sixth embodiment of the present invention;

[0029]FIG. 10 is a view of the configuration of a machine tool to whichthe tool management system is applied; and

[0030]FIG. 11 is a view of the configuration of an electrical system ofa tool and the configuration of a tool management system using the sameaccording to a seventh embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] Below, an explanation will be made of embodiments of the presentinvention by referring to the drawings.

[0032] First Embodiment

[0033]FIG. 1 is a view of the configuration of a machining center as anexample of a machine tool according to the present invention. Note thatthe machining center is a numerical control machine tool capable ofso-called combined machining.

[0034] In FIG. 1, the machining center 1 is provided with a cross rail37 having two ends movably supported by shafts of a double housing typecolumn 38. A ram 45 is provided movably in a vertical direction (Z-axisdirection) via a saddle 44 supported movably on this cross rail 37.

[0035] The saddle 44 is provided with a not illustrated nut part passingthorough the cross rail 37 in a horizontal direction. A feed shaft 41with a screw part formed on the outer circumference is screwed into thisnut part.

[0036] A servo motor 19 is connected with an end of the feed shaft 41.The feed shaft 41 is driven to rotate by the servo motor 19.

[0037] By the rotation of the feed shaft 41, the saddle 44 moves in theY-axis direction. By this, the ram 45 is moved and positioned in theY-axis direction.

[0038] Further, the saddle 44 is provided with a not illustrated nutpart in the vertical direction. The feed shaft 42 with a screw partformed on the outer circumference is screwed into this nut part. A servomotor 20 is connected with an end of the shaft 42.

[0039] The servo motor 20 drives the feed shaft 42 to rotate. By this,the ram 45 movably provided on the saddle 44 is moved and positioned inthe Z-axis direction.

[0040] The ram 45 has built into it a spindle motor 31. This spindlemotor 31 rotates a spindle 46 rotatably supported by the ram 45. A toolT such as an end mill is attached at the front end of the spindle 46.The tool is driven by the rotation of the spindle 46.

[0041] Below the ram 45, a table 35 is provided movably in the X-axisdirection. The table 35 is provided with a not illustrated nut part. Anot illustrated nut feed shaft provided along the X-axis direction isscrewed into this nut part. This not illustrated feed shaft is connectedto the servo motor 20.

[0042] The table 35 is moved and positioned in the X-axis direction bythe rotation and driving of the servo motor 18.

[0043] Further, the double housing column 38 is provided with a notillustrated nut part. The cross rail 37 is raised and lowered by therotation of the feed shaft 32 a screwed into it by a cross railelevation motor 32.

[0044] An automatic tool changer (ATC) 39 automatically changes the toolT attached to the spindle 46.

[0045] That is, the automatic tool changer 39 holds various tools in itsnot illustrated magazine, returns the tool T attached to the spindle bya not illustrated tool changing arm into the magazine, and attaches arequired tool held by the magazine to the spindle by the tool changingarm.

[0046] A numerical control apparatus 51 drives and controls the aboveservo motors 18, 19, and 20, the cross rail elevation motor 32, and thespindle motor 31.

[0047] Specifically, the numerical control apparatus 51 controls thepositions and the speeds between a workpiece and the tool T by the servomotor 18, 19, and 20 according to a machining process defined in advancein a machining program. Further, the numerical control apparatus 51controls the rotational speed of the spindle 46 by decoding therotational speed of the spindle 46 defined by an S-code in the machiningprogram. Still further, the numerical control apparatus 51 automaticallychanges various tools by decoding the tool changing operation of thetool T defined by for example an M-code in the machining program.

[0048]FIG. 2 is a sectional view of a tool according to the firstembodiment of the present invention.

[0049] In FIG. 2, a tool 60 is comprised of a cutting tool 100 and atool holder 61. Note that the cutting tool 100 is an embodiment of amachining tool according to the present invention.

[0050] The tool holder 61 has an attachment part 62, a casing 65comprised of casing parts 66, 67, and 68, a generator 70, an electricmotor 80, a tool holding part 90, and a locking part 85.

[0051] The attachment part 62 is provided with a grip part 62 a, a tapershank 62 b to be attached to a taper sleeve 46 a formed at the front endof the above spindle 46, a pull stud 62 c formed at the front end ofthis taper shank 62 b, and a shaft portion 62 d rotatably held by thecasing part 66.

[0052] The grip part 62 a of the attachment part 62 is gripped by theabove tool changing arm of the automatic tool changer 39 when the tool60 is being attached to the spindle 46 from the magazine of theautomatic tool changer 39 and when the tool 60 is being conveyed fromthe spindle to the magazine of the automatic tool changer 39.

[0053] The center of the taper shank 62 b of the attachment part 62becomes concentric with the center of the spindle 46 by being attachedto the taper sleeve 46 a of the spindle 46.

[0054] The pull stud 62 c of the attachment part 62 is clamped by acollet of a not illustrated clamping mechanism built in the spindle 46when the attachment part 62 is attached to the taper sleeve 46 a of thespindle 46. Note that the clamping mechanism built in the spindle 46 iswell known, so a detailed explanation of it will be omitted.

[0055] The shaft portion 62 d of the attachment part 62 is supportedrotatably held by the inner circumference of the casing part 66 via aplurality of bearings 72.

[0056] The shaft portion 62 d of the attachment part 62 is connectedwith the input shaft 71 of the generator 70. As this generator 70, forexample, a three-phase synchronous generator can be used.

[0057] The electric power generated by the generator 70 is supplied tothe electric motor 80. As this electric motor 80, for example, athree-phase induction motor can be used.

[0058] For example, in a case where a three-phase synchronous generatoris used as the generator 70 and a three-phase induction motor is used asthe electric motor 80, as shown in FIG. 3, the generator 70 and theelectric motor80 are connected by three power cables Wx, WY, and Wz. Theelectric motor 80 receives a supply of three-phase alternating currentgenerated by the generator 70 through the three power cables.

[0059] The tool holding part 90 has a rotatable shaft 91, a coupling 93for connecting this rotatable shaft 91 and the output shaft 81 of theelectric motor 80, and a tool attachment part 95.

[0060] The rotatable shaft 91 is rotatably held by the innercircumference of the casing part 68 via a plurality of rolling bearings72.

[0061] The front end side of the rotatable shaft 91 is prevented fromdetaching from the casing part 68 by a stopper 94.

[0062] The cutting tool 100 is held by the tool attachment part 95. Thiscutting tool 100 machines a workpiece.

[0063] Specifically, as the cutting tool 100, a cutting tool such as adrill or an end mill may be used.

[0064] The casing parts 66, 67, and 68 are connected each other byclamping means such as bolts. The casing 65 is constructed by thesecasing parts 66, 67, and 68.

[0065] A locking part 85 is mounted on the outer circumference of thecasing part 66.

[0066] When the attachment part 62 is attached to the taper sleeve 46 aof the spindle 46, the front end of the locking part 85 is inserted toan engagement hole 47 a formed at a non-rotating part such as the ram 45on the side of the spindle 46.

[0067] Due to this, even if the spindle 46 is rotated, rotation of thecasing 65 is prevented.

[0068] Next, an explanation will be made of an example of the operationof the above configured tool 60.

[0069] First, the automatic tool changer 39 attaches the tool holder 61holding the cutting tool 100 at the tool attachment holder 95 to thespindle 46 of the machining center 1. The front end 85 a of the lockingpart 85 is inserted into the engagement hole 47 a of the non-rotatingpart 47 whereby the rotation of the casing 65 is prevented.

[0070] By rotating the spindle at the rotational speed of No from thisstate, the attachment part 62 of the tool holder 61 is rotated, and therotation of the spindle 46 is transmitted to the generator 70. By this,the generator 70 generates electric power. In the case of a three-phasesynchronous generator as the generator 70, the generator 70 generatesthree-phase alternating current.

[0071] The frequency F of the three-phase alternating current generatedby the generator 70, as the pole number of the generator 70 is P₁ andthe rotational speed of the spindle 46 is No [rpm], is expressed by thefollowing formula (1).

F=p ₁ *N ₀/120 [Hz]  (1)

[0072] Accordingly, when the spindle 46 is rotated at the rotationalspeed N₀, a three-phase alternating current having the frequency Fexpressed the above formula (1) is supplied to the electric motor 80.

[0073] Here, in case where a three-phase induction motor is used as theelectric motor 80, as the pole number of the electric motor 80 is p₂,the electric motor 80 is rotated by 2/p₂ per cycle of the three-phasealternating current.

[0074] Therefore, the synchronous rotational speed of the electric motor80 is expressed by the following formula (2).

N ₁=120*F/p ₂  (2)

[0075] Accordingly, the relationship of the rotational speed N₁ of thecutting tool 100 to the rotational speed N₀ of the spindle 46 isexpressed by the following formula (3).

N ₁ =N ₀ *p ₁ /p _(2 [) rpm]  (3)

[0076] As understood from formula (3), the rotational speed N₀ of thespindle 46 is changed to the rotational speed N₁ expressed by the aboveformula (3).

[0077] As expressed by the formula (3), it is found that byappropriately setting the ratio between the pole number p₁ of thegenerator 70 and the pole number p₂ of the electric motor 80, it ispossible to freely set the ratio of the rotational speed of the cuttingtool 100 to the rotational speed of the spindle 46.

[0078] That is, in the case where it is intended to raise the rotationalspeed of the cutting tool 100 higher than that of the spindle 46, theratio of the pole number p₁/p₂ is set larger than 1. When it is intendedto reduce the rotational speed of the cutting tool 100 to lower thanthat of the spindle 46, the ratio of the pole number p₁/p₂ is setsmaller than 1.

[0079] Next, an explanation of the driving method of the aboveconfigured tool will be made.

[0080] When machining a workpiece comprised of a difficult-to-cutmaterial such as aluminum alloy, sometimes the rotational speed of thecutting tool 100 is raised higher than the maximum rotational speed ofthe spindle 46.

[0081] In such a case, the tool 60 is held in advance in the magazine ofthe automatic tool changer 39 of the machining center 1.

[0082] For example, when the maximum rotational speed Nmax of thespindle 46 of the above machining center 1 is 3000 rpm and therotational speed of the cutting tool 100 is raised to 30,000 rpm, thegenerator 70 and the electric motor 80 having a ratio of the pole numberp₁/p₂ of 10 are used.

[0083] The automatic tool changer 39 attaches the tool 60 automaticallyto the spindle 46 in the same way as an ordinary tool. Note that anordinary tool is a tool having a cutting tool clamped by a tool holder.

[0084] The rotational speed of the cutting tool 100 held by the toolholder 61 is controlled by the rotational speed of the spindle 46.Specifically, in the machining program downloaded in the numericalcontrol apparatus 51, the rotational speed of the spindle 46 isdesignated in advance by an S-code in accordance with the rotationalspeed of the cutting tool 100 held by the tool holder 61. For example,when rotating the cutting tool 100 at the rotational speed of 30,000rpm, the rotational speed of the spindle 46 is designated as 3000 rpm bythe S-code in the machining program.

[0085] When the spindle 46 is rotated at the rotational speed of 3000rpm, the generator 70 generates a three-phase alternating current havinga frequency in accordance with the rotational speed of the spindle 46and the pole number of the generator 70 and electric motor 80.

[0086] The electric motor 80 is driven by the three-phase alternatingcurrent supplied from the generator 70, while the cutting tool 100 heldby the tool holder 61 is rotated at the rotational speed of about 30,000rpm.

[0087] In the above state where the rotational speed of the cutting tool100 is increased, by moving the workpiece fixed on the table 35 relativeto the cutting tool 100 (spindle 46) in accordance with the machiningprogram, the workpiece is cut.

[0088] By this, it becomes possible to appropriately cut a workpiececomprised of a difficult-to-cut material such as aluminum alloy.

[0089] In this way, according to the present embodiment, the rotationalspeed of the cutting tool 100 is raised by driving the motor 80 by theelectric power generated by the generator 70. Due to this, even if thespindle 46 is rotated at a high rotational speed, heat is notincreasingly generated such as in a gear apparatus, so a reduction ofthe machining tolerance due to the heat can be avoided.

[0090] Further, in this embodiment, the rotational speed of the cuttingtool 100 is changed by using the generator 70 and electric motor 80.Therefore, it is possible to decrease the cost and noise of the tool 60compared with the case using a transmission mechanism such as a gearapparatus.

[0091] Further, according to this embodiment, the tool 60 can beattached to the spindle 46 and changed by the automatic tool changer 39in the same way as an ordinary tool. Due to this, it is possible toimmediately respond to a need for high speed rotation of the cuttingtool 100.

[0092] Further, according to this embodiment, the cutting tool 100 isdriven by the electric power generated by the rotation of the spindle46. For this reason, it is not necessary to supply electric power fromoutside of the tool, so a cable for supplying electric power is notnecessary between the spindle 46 and the tool 60.

[0093] Further, in this embodiment, a three-phase synchronous generatoris used as the generator 70 and a three-phase induction motor is used asthe electric motor 80. Due to this, it becomes possible to easilycontrol the rotational speed of the-cutting tool 100 by the rotationalspeed of the spindle 46. That is, since the three-phase synchronousgenerator generates voltage having a frequency precisely proportional tothe rotational speed of the spindle 46 and since the three-phaseinduction motor drives the cutting tool 100 at a rotational speedproportional to this frequency, the rotational speed of the cutting tool100 can be easily and precisely controlled by the rotational speed ofthe spindle 46 and the pole number ratio between the three-phasesynchronous generator and the three-phase induction motor.

[0094] Further, no position detecting element for detecting therotational position of a rotor is needed for the electric motor 80. Dueto this, no cable is needed between the numerical control apparatus 51and the tool holder 51, so complete separation of the tool 60 from thespindle 46 becomes possible.

[0095] Note that in the above embodiment, the explanation was made ofthe case of application to high speed machining of an aluminum alloy,but the present invention can be applied to any machining requiringacceleration of the rotational speed of the spindle 46. For example, thepresent invention can be applied to machining of various superdifficult-to-cut materials such as cemented carbide, silicate glass, andceramics.

[0096] Further, in the above embodiment, the explanation was made of thecase of increasing the rotational speed of the cutting tool 100 from therotational speed of the spindle 46, but decreasing the rotational speedof the cutting tool 100 from the rotational speed of the spindle 46 isalso possible.

[0097] Further, in the above embodiment, the explanation was made of thecase of use of a three-phase synchronous generator as the generator 70and use of a three-phase induction motor as the electric motor 80, butit is also possible to employ a configuration changing the rotationalspeed of the spindle 46 by a combination of a direct current generatorand a direct current motor. The rotational speed of the direct currentmotor is determined by voltage supplied from the direct currentgenerator and the load. For this reason, it is difficult to directlycontrol the rotational speed of the cutting tool 100 by the rotationalspeed of the spindle 46.

[0098] By measuring the output characteristic and the loadcharacteristic of the direct current generator and the direct currentmotor in advance, it becomes possible to change the rotational speed ofthe spindle 46 at a constant speed ratio by the combination of thedirect current generator and the direct current motor.

[0099] Further, it is possible to use another kind of generator andmotor.

[0100] Second Embodiment

[0101]FIG. 4 is a view of the configuration of the electrical system ofa tool according to a second embodiment of the present invention. Notethat the mechanical structure of the tool according to the presentembodiment is the same as the above mentioned embodiment.

[0102] As shown in FIG. 4, the tool according to the present embodimentis provided with an alternating current generator as the generator 70, adirect current motor as the electric motor 80, and a rectifier circuit201.

[0103] The rectifier circuit 201 rectifies alternating current generatedby the generator 70 and supplies it to the electric motor 80. Thisrectifier circuit 201 is built in, for example, the above casing 65.

[0104] The amount of the direct current supplied from the rectifiercircuit 201 is defined by the rotational speed of the spindle 46. On theother hand, the rotational speed of the direct current motor can becontrolled in accordance with the amount of the supplied current.Accordingly, by controlling the rotational speed of the spindle 46,control of the speed of the electric motor 80 becomes possible.

[0105] In this way, according to the present invention, even if analternating current generator is used as the generator 70 and a directcurrent motor is used as the electric motor 80, by providing therectifier circuit 201 at the tool, it is possible to change therotational speed of the cutting tool 100 from the rotational speed ofthe spindle 46.

[0106] Note that in the above embodiment, a configuration where therectifier circuit 201 was built in the casing 65 was employed, but it isalso possible to employ a configuration where the rectifier circuit 201is housed in a box or the like and this is attached to the outside ofthe casing 65.

[0107] Further, it is also possible to employ a configuration where acavity is formed at the casing 65 and the cavity houses the rectifiercircuit 201.

[0108] Third Embodiment

[0109]FIG. 5 is a view of the configuration of the electrical system ofa tool according to a third embodiment of the present invention. Notethat the mechanical structure of the tool according to the presentembodiment is the same as the above mentioned first embodiment.

[0110] In the above first and second embodiments, the rotational speedof the cutting tool 100 of the tool 60 is controlled by the rotationalspeed of the spindle 60, namely, the input rotational speed of thegenerator 70.

[0111] In the present embodiment, an explanation will be made of aconfiguration enabling control of the rotational speed of the cuttingtool 100 regardless of the input rotational speed of the generator 70.

[0112] As shown in FIG. 5, the tool according to the present embodimentis provided with a generator 70 comprised of an alternating currentgenerator, an electric motor 80, a rectifier circuit 302, an inverter303, and a control circuit 304.

[0113] The rectifier circuit 302, the inverter 303, and the controlcircuit 304 are incorporated in the above casing 65. Note that it ispossible to employ a configuration where at least some of theserectifier circuit 302, inverter 303, and control circuit 304 are housedin a box mounted on the outside of the casing 65.

[0114] Further, it is also possible to employ a configuration where acavity is formed on the casing 65 and the cavity houses these rectifiercircuit 302, inverter 303, and control circuit 304.

[0115] Further, the rectifier circuit 302 supplies part of the rectifieddirect current to the control circuit 304.

[0116] The inverter 303 changes the direct current supplied from therectifier circuit 302 into alternating current for driving the electricmotor 80. For example, the inverter 303 is configured by a pulse widthmodulation (PWM) inverter.

[0117] The control circuit 304 is provided with a microprocessor 305, aread only memory (ROM) 306, a random access memory (RAM) 307, a countercircuit 308, an analog-to-digital (A/D) converter 310, and adigital-to-analog (D/A) converter 309.

[0118] The ROM 306 stores a control program for controlling the electricmotor 80. The control program performs for example variable speedcontrol of the electric motor 80 by field-oriented control.

[0119] The RAM 307 stores data for operations of the microprocessor 305.

[0120] The microprocessor 305 executes the control program stored in theROM 306, performs various operations, and outputs control signals 304 sto the inverter 300 via the D/A converter 309. The control signals 304 sare for example PWM control signals.

[0121] The A/D converter 310 converts the value of the current suppliedfrom the inverter 303 to the electric motor 80 detected by a currentdetector 312 into a digital signal.

[0122] The electric motor 80 is provided with a rotational positiondetector 311. As this rotational position detector 311, for example, anoptical rotary encoder or a resolver may be used.

[0123] The counter circuit 308 counts pulse signals detected by therotational position detector 311 in accordance with the rotation of theelectric motor 80 and outputs the count to the microprocessor 305.

[0124] The above configured control circuit 304 can operate by receivingelectric power generated by the generator 70 by the rotation of thespindle 46.

[0125] The control circuit 304 receives the rotation and the drivecurrent of the electric motor 80 as input. Due to this, by preparing adesired control program in the ROM 306 of the control circuit 304 inadvance, various control of the electric motor 80 becomes possible.

[0126] For example, when a synchronous motor is used as the electricmotor 80 and it is intended to variably control the speed of thissynchronous motor, velocity reference data is set in advance in the ROM306. By this, speed control of the electric motor 80 becomes possible inaccordance with this velocity reference data.

[0127] Accordingly, according to the present embodiment, control of therotational position, the rotational speed, and the torque of the cuttingtool 100 becomes possible regardless of the rotational speed of thespindle 46. That is, in the present embodiment, it becomes possible todrive and control the cutting tool 100 separately at the tool side.

[0128] Fourth Embodiment

[0129]FIG. 6 is a view of the configuration of the electrical system ofa tool according to a fourth embodiment of the present invention. Notethat the mechanical structure of the tool according to the presentembodiment is the same as the above mentioned first embodiment.

[0130] The point of difference between the configuration of the presentembodiment and the configuration explained in the third embodiment isthat the generator 70 is provided with a rotational position detector402 and the signal detected by this rotational position detector 402 isinput to the microprocessor 305 via a counter circuit 403. The rest ofthe configuration of the present embodiment is exactly the same as thatof the third embodiment.

[0131] The rotational position detector 402 is mounted to the inputshaft 71 of the generator 70 and detects the rotation of the input shaft71. As the rotational position detector 402, for example, an opticalrotary encoder or a resolver may be used.

[0132] By detecting the amount of rotation of the input shaft 71 by therotational position detector 402, the rotation of the spindle 46 isinput to the control circuit 304.

[0133] In the control circuit 304, by calculating the difference perunit time of the rotation received from the counter circuit 403, itbecomes possible to determine the rotational speed of the spindle 46.

[0134] Accordingly, by preparing in advance a program for generatingvelocity references having a constant speed ratio to the rotationalspeed of the spindle 46 in the ROM 306, it becomes possible toaccurately control the rotational speed of the electric motor 80 withrespect to that of the spindle 46. That is, by employing theconfiguration of the present embodiment, it becomes possible toaccurately control the rotational speed of the spindle 46 in the sameway as a gear apparatus.

[0135] Further, in the control circuit 304, both of the rotationalposition of the spindle 46 and the rotational position of the electricmotor 80 can be obtained, so it becomes possible to make the rotationalposition of the spindle 46 and the rotational position of the electricmotor 80 exactly match.

[0136] Fifth Embodiment

[0137]FIG. 7 is a view of a configuration of the electrical system of atool according to a fifth embodiment of the present invention.

[0138] Note that the mechanical structure of the tool according to thepresent embodiment is the same as the above mentioned first embodiment.

[0139] The point of difference between the configuration of the presentembodiment shown in FIG. 7 and the configuration explained in the thirdembodiment is that a data input unit 501 is added to the control circuit304. The rest of the configuration of the present embodiment is exactlythe same as that of the third embodiment.

[0140] The data input unit 501 inputs various types of data forcontrolling the electric motor 80 from the outside to the controlcircuit 304.

[0141] Specifically, the data input unit 501 can be configured byswitches mounted on the casing 65 which are operable from outside thecasing 65.

[0142] The data input unit 501 can be also configured by a receivingapparatus mounted on the outside of the casing 65 for receiving wirelesssignals. According to this configuration, it becomes possible to inputdata in real time while machining by the tool.

[0143] The data input from the data input unit 501 includes for examplevarious types of data such as velocity references to the electric motor80 or control parameters.

[0144] In the present embodiment, by employing the above configuration,it is possible to freely change the content of the control of theelectric motor 80. For example, when machining conditions are changed,it becomes possible to easily change the rotational speed of theelectric motor 80.

[0145] Sixth Embodiment

[0146]FIG. 8 is a sectional view of a tool according to a sixthembodiment of the present invention. Note that in FIG. 8, partscorresponding to those in the tool 60 according to the first embodimentare assigned the same reference numerals.

[0147] The tool 160 shown in FIG. 8 is configured from the cutting tool100 and a tool holder 161.

[0148] The tool holder 161 is provided with a secondary battery 110, aprocessing board 300, and an antenna 141 in addition to the attachmentpart 62, the casing 65, the generator 70, the electric motor 80, thetool holding part 90, and the locking part 85.

[0149] The secondary battery 110 is fixed inside of the casing part 67.This secondary battery 110 stores part of the electric power generatedby the generator 70. As the secondary battery 110, for example, anickel-cadmium battery may be used. Besides this, a nickel-hydrogenbattery, a lithium battery, or a small-sized lead storage battery can bealso used.

[0150] The antenna 141 is fixed on the outside surface of the casingpart 65.

[0151] The processing board 300 is fixed inside of the casing 65. Thisprocessing board 300 is electrically connected with the secondarybattery 110 and antenna 141.

[0152]FIG. 9 is a view of the configuration of the electrical system ofthe tool and the configuration of the tool management system accordingto the sixth embodiment of the present invention.

[0153] In FIG. 9, the tool 160 is provided with a charging circuit 120,a processing circuit 150, and a transmitting and receiving circuit 140in addition to the above generator 70, the electric motor 80, thesecondary battery 110, and the antenna 141.

[0154] Further, the tool management system according to the presentembodiment is comprised of the tool 160 and a management apparatus 400.

[0155] The charging circuit 120, the processing circuit 150, and thetransmitting and receiving circuit 140 are formed on the aboveprocessing board 300. The charging circuit 120 charges the secondarybattery 110 with a part of the electric power generated by the generator70. This charging circuit 120 is comprised of a rectifier circuit forrectifying the alternating voltage generated by the generator 70, asmoothing circuit for smoothing the ripple included in the outputvoltage of this rectifier circuit and converting it into appropriatevoltage, etc.

[0156] The secondary battery 110 supplies the electric power charged bythe charging circuit 120 to the power receiving part 170 having theprocessing circuit 150 and the transmitting circuit 150.

[0157] The processing circuit 150 operates by receiving the electricpower supplied from the secondary battery 110 and processes informationrelated to the machining of a workpiece by the cutting tool 100.

[0158] Here, the information related to the machining of a workpiece bythe cutting tool 100 includes, for example, tool information of apredetermined format for identifying the tool 160, monitor informationconcerning the rotational state of the generator 70 or the electricmotor 80 during machining, etc. Further, the information related to themachining of a workpiece by the cutting tool 100 also includesinformation about the detected rotational position and the detectedrotational speed of the electric motor 80.

[0159] The tool information includes for example information about thetype of the cutting tool 100 such as drill or end mill, size of thecutting tool 100 such as diameter or length, etc.

[0160] The monitor information includes information about disconnectionor short-circuits of cables in the generator 70 or the electric motor80, overload of the electric motor 80, etc.

[0161] The processing circuit 150 first generates the above toolinformation of the predetermined format. Further, the processing circuit150 detects the generated current 70 s of the generator 70 or drivecurrent 80 s of the electric motor 80, monitors for an irregular stateof the generator 70 or the electric motor 80 based on the detectedinformation, adds this monitor information to the tool information, andtransmits this tool information to the transmitting and receivingcircuit 140.

[0162] The transmitting and receiving circuit 140 transmits the datafrom the processing circuit 150 to the management apparatus 400 as awireless signal by the antenna 141.

[0163] The charging circuit 120, the processing circuit 150, and thetransmitting and receiving circuit 140 can be incorporated in the casing65. Note that it is also possible to house the processing circuit 150and the transmitting and receiving circuit 140 in a box and mount thebox to the outside of the casing 65. Further, it is also possible toemploy a configuration where a cavity is formed on the casing 65 and thecharging circuit 120 and the processing circuit 150 and the transmittingand receiving circuit 140 are housed in the cavity.

[0164] The management apparatus 400 is provided with an antenna 401which receives data from the antenna 141. This management apparatus 400is provided with a utility program for monitoring and managing the tool160 based on the data from the antenna 141. Note that the managementapparatus 400 is configured by for example a personal computer.

[0165] Further, as shown in FIG. 10, the management apparatus 400 isconnected to the numerical control apparatus 51. In a case of anirregular state such as a fault in the tool 160, the managementapparatus 400 transmits this irregular state information to thenumerical control apparatus 51.

[0166] Next, an explanation will be given of an example of the operationof the above configured tool 160.

[0167] The automatic tool changer 39 attaches the tool holder 161holding the cutting tool 100 to the spindle 46 of the machining center1. The front end 85 a of the locking part 85 is inserted into theengagement hole 47 a of the non-rotating part 47, whereby rotation ofthe casing 65 is prevented.

[0168] When the spindle 46 is rotated at predetermined rotational speedfrom this state, the attachment part 62 of the tool holder 161 isrotated, so the rotation of the spindle 46 is transmitted to thegenerator 70.

[0169] For example, in case where a three-phase synchronous is used asthe generator 70, three-phase alternating current is generated.

[0170] A part of this three-phase alternating current is charged intothe secondary battery 110 by the charging circuit 120.

[0171] The processing circuit 150 and the transmitting and receivingcircuit 140 become operable by the charge of the secondary battery 110.

[0172] When the processing circuit 150 becomes operable, the processingcircuit 150 generates the tool information of a predetermined format andtransmits this tool information to the transmitting and receivingcircuit 140.

[0173] The transmitting and receiving circuit 140 transmits the toolinformation of a predetermined format to the management apparatus 400.

[0174] When an irregular state of the generator 70 or the electricalmotor 80 occurs while machining a workpiece by the cutting tool 100,irregular state information is transmitted to the management apparatus400 in addition to the tool information.

[0175] Further, if the secondary battery is charged, even after therotation of the spindle 46 stops, the processing circuit 150 and thetransmitting and receiving circuit 140 can transmit various types ofdata such as tool information or irregular state information to themanagement apparatus 400.

[0176] For example, when the management apparatus 400 has obtained theirregular state information from the transmitting and receiving circuit140, the management apparatus 400 transmits this irregular stateinformation to the numerical control apparatus 51. When receiving theirregular state information, the numerical control apparatus 51 controlsthe automatic tool changer 39 so as to detach the tool 160 from thespindle 46.

[0177] According to the present embodiment, the tool 160 is providedwith the secondary battery 110 and can use the electric power stored inthis secondary battery 110 in the power receiving part 170 other thanthe electric motor 80. Due to this, it is possible to operate variouscircuits incorporated in or added to the tool 160 regardless of therotation of the spindle 46, and it is possible to transmit and receivedata even during stoppage of the spindle 46.

[0178] Further, according to the present embodiment, by the managementapparatus 400 collecting information from the tool 160, comprehensivemanagement of the tool 160 becomes possible.

[0179] Seventh Embodiment

[0180]FIG. 11 is a view of the configuration of the electrical system ofa tool and the configuration of a tool management system according to aseventh embodiment of the present invention.

[0181] Note that the mechanical structure of the tool according to thepresent embodiment is the same as the sixth embodiment. In FIG. 11, theparts corresponding to those in the tool 160 according to the sixthembodiment use the same reference numerals.

[0182] In the above sixth embodiment, the management apparatus 400 onlyreceived the data from the tool 160, but in the present embodiment, anexplanation will be made of a configuration enabling transmission andreception of data between the management apparatus 400 and the tool 260.

[0183] As shown in FIG. 11, the tool 260 according to the presentembodiment is provided with a rectifier circuit 200, an inverter 210,and a power receiving part 270 in addition to the generator 70 comprisedof an alternating current generator, the electric motor 80 comprised ofan induction motor, the secondary battery 110, and the charging circuit120.

[0184] Further, the rectifier circuit 200, the inverter 210, and thepower receiving part 270 are housed in the casing 65. Note that it ispossible to employ a configuration where at least some or theserectifier circuit 200, inverter 210, and power receiving part 270 arehoused in a box mounted on the outside of the casing 65.

[0185] Further, it is also possible to employ a configuration where acavity is formed in the casing 65, and the rectifier circuit 200, theinverter 210, and the power receiving part 270 are housed in the cavity.

[0186] The rectifier circuit 200 rectifies alternating current generatedby the generator 70 and supplies it to the inverter 210.

[0187] The inverter 210 changes the supplied direct current from therectifier circuit 200 to alternating current for driving the electricmotor 80. For example, the inverter 210 is comprised of a PWM inverter.

[0188] The charging circuit 120 charges the secondary battery 110 withpart of the electric power generated by the generator 70. This chargingcircuit 120 is comprised of a rectifier circuit for rectifying thealternating voltage generated by the generator 70, a smoothing circuitfor smoothing the ripple included in the output of this rectifiercircuit and converting it into appropriate voltage, etc.

[0189] The secondary battery 110 supplies the electric power charged bythe charging circuit 120 to the electric power receiving part 270.

[0190] The electric power receiving part 270 is comprised of aprocessing circuit part 504 and the transmitting and receiving circuit240 and is operated by electric power supplied from the secondarybattery 110.

[0191] The transmitting and receiving circuit 240 transmits the datarelated to machining of a workpiece by the cutting tool 100 to themanagement apparatus 400 and receives data related to machining of aworkpiece by the cutting tool 100 from the management apparatus 400 viaan antenna 241.

[0192] The processing circuit part 504 processes the information relatedto machining of a workpiece by the cutting tool 100. This processingcircuit part 504 is provided with a microprocessor 505, a read onlymemory (ROM) 506, a random access memory (RAM) 507, a counter circuit508, an analog-to-digital(A/D) converter 510, and a digital-to-analogconverter 509.

[0193] The ROM 506 stores a control program for controlling the electricmotor 80. The control program performs for example variable speedcontrol of the electric motor 80 by field-oriented control. Further, theROM 506 stores a program for generating tool information of apredetermined format or monitoring an irregular state of the tool, aprogram for transmitting various types of data to the transmitting andreceiving circuit 240 and receiving various types of data from thetransmitting and receiving circuit 240, etc.

[0194] The RAM 507 stores data for operations of the microprocessor 505,data transmitted from the transmitting and receiving circuit 240, etc.

[0195] The microprocessor 505 executes the control program stored in theROM 506. Specifically, the microprocessor 505 performs variousoperations, outputs control signals 504 s to the inverter 210 via theD/A converter 509, transmits data to the transmitting and receivingcircuit 240, and receives data from the transmitting and receivingcircuit 240. The control signals 504 s are for example PWM controlsignals.

[0196] The A/D converter 510 converts values detected by a currentdetector 312 of the current supplied from the inverter 210 to theelectric motor 80 into a digital signal.

[0197] The electric motor 80 is provided with a rotational positiondetector 311. As this rotational position detector 311, for example, anoptical rotary encoder or a resolver may be used.

[0198] The counter circuit 508 counts pulse signals detected by therotational position detector 311 in accordance with the rotation of theelectric motor 80 and transmits the count as output to themicroprocessor 305.

[0199] When the tool 260 is attached to the spindle 46 and the spindle46 is rotated, the secondary battery 110 is charged by the chargingcircuit 120. By this, the power receiving part 270 becomes operable bythe electric power supplied from the secondary battery 110.

[0200] The rotation and the drive current of the electric motor 80 arefed back to the processing circuit part 504, so by preparing in advancea desired program in the ROM 506 of the processing circuit part 504,various control of the electric motor 80 becomes possible.

[0201] Further, it is also possible to transmit this control program tothe tool 260 from the management apparatus 400, receive this by thetransmitting and receiving circuit 240, and store it in the RAM 507.

[0202] The microprocessor 505 generates tool information of apredetermined format and transmits the information to the managementapparatus 400 through the transmitting and receiving circuit 240. Themanagement apparatus 400 manages this tool information.

[0203] Further, the information of the rotational position and the drivecurrent of the electric motor 80 are fed back to the microprocessor 505,so it is also possible to transmit sequentially this feedbackinformation to the management apparatus 400 together with the above toolinformation.

[0204] The management apparatus 400 can monitor data such as therotational speed and the torque of the cutting tool 100. Due to this, itbecomes possible to detect an irregular state such as breakage of thecutting tool 100 in real time based on the monitored various data.Further, it also becomes possible to easily manage the time used formachining.

[0205] Further, the microprocessor 505 of the processing circuit part504 monitors the state of the generator 70 and the electric motor 80.When an irregular state occurs, it transmits this irregular stateinformation to the management apparatus 400. When obtaining theirregular state information, the management apparatus 400 transmits thisirregular state information to the numerical control apparatus 51. Whenthe irregular state information is transmitted, the numerical controlapparatus 51 controls the automatic tool changer 39 so as to detach thetool 260 from the spindle 46.

[0206] As described above, according to the present embodiment, byproviding a program for controlling the tool 260 in the processingcircuit part 504, it becomes possible to control the tool 260 separatelyfrom the spindle 46.

[0207] Further, by transmitting a program from the management apparatus400 to the tool 260 and transmitting not only the simple toolinformation but various state information while machining to themanagement apparatus 400, it becomes possible to precisely manage thetool 260.

[0208] While the invention has been described by the reference tospecific embodiments chosen for purpose of illustration, it should beapparent that numerous modification could be made thereto by thoseskilled in the art without departing from the basic concept and scope ofthe invention.

[0209] For example, in the above embodiments, the explanation was givenwith reference to a cutting tool 100 as a machining tool, but thepresent invention can also be applied to other machining tools such as agrinding wheel, a polishing tool, or the like.

What is claimed is:
 1. A tool attachable to a spindle of a machine tool comprising: a machining tool for machining a workpiece; an electric motor for driving said machining tool; and a generator for generating electric power to drive said electric motor by the rotation of said spindle.
 2. A tool as set forth in claim 1 , wherein said generator and said electric motor change the rotational speed of said machining tool from the rotational speed of said spindle by a predetermined ratio determined based on a pole number of said generator and electric motor.
 3. A tool as set forth in claim 2 , wherein said generator is an alternating current generator which supplies current with a frequency in accordance with the rotational speed of said spindle to said electric motor; and said electric motor is an induction motor which rotates at a rotational speed in accordance with said frequency.
 4. A tool as set forth in claim 3 , wherein said generator is a three-phase synchronous generator; and said electric motor is a three-phase induction motor.
 5. A tool as set forth in claim 1 , further comprising: a tool attachment part attachable to said spindle for transmitting the rotation of said spindle to said generator; a tool holding part for rotatably holding said machining tool; a casing for holding said electric motor, said generator, said tool attachment part, and said tool holding part; and a locking part for preventing rotation of said casing by engagement with a non-rotating part of said machine tool.
 6. A tool attachable to a spindle of a machine tool comprising: a machining tool for machining a workpiece; an electric motor for driving said machining tool; a generator for generating electric power to drive said electric motor by the rotation of said spindle; and a control means for controlling a supply of electric power generated by said generator to drive and control said machining tool.
 7. A tool as set forth in claim 6 , wherein said control means comprises: a memory for storing a program for driving and controlling said machining tool; a processor for performing said program; and a driving circuit for supplying the electric power from said generator to said electric motor in respond to a control signal from said processor.
 8. A tool as set forth in claim 6 , further comprising a rotation detecting means for detecting a rotational position and/or rotational speed of said electric motor; wherein said control means controls said electric motor based on the detected rotational position and/or the detected rotational speed.
 9. A tool as set forth in claim 6 , further comprising: a rotation detecting means for detecting a rotational position and/or rotational speed of said electric motor; and a rotation detecting means for detecting a rotational position and/or rotational speed of said spindle; and said control means controls said electric motor based on the detected rotational position and/or rotational speed of both of said spindle and electric motor.
 10. A tool as set forth in claim 6 , further comprising: a data input means for inputting various data required for controlling said electric motor to said controlling means from the outside.
 11. A tool attachable to a spindle of a machine tool comprising: a machining tool for machining a workpiece; an electric motor for driving said machining tool; a generator for generating electric power to drive said electric motor by the rotation of said spindle; an electric power receiving part other than said electric motor for receiving supply of the electric power; a secondary battery able to supply power to said electric power receiving part; and a charging circuit for charging said secondary battery with part of the electric power generated by said generator.
 12. A tool as set forth in claim 11 , further comprising: a processing circuit, operated by electric power supplied from said secondary battery, for processing data related to machining of the work by said machining tool.
 13. A tool as set forth in claim 11 further comprising a transmitting and receiving circuit, operated by electric power supplied from said secondary battery, for performing at least one of transmission and reception of a wireless signal indicating information related to machining of a workpiece by said machining tool.
 14. A tool attachable to a spindle of a machine tool comprising: a machining tool for machining a workpiece; an electric motor for driving said machining tool; a generator for generating electric power to drive said electric motor by the rotation of said spindle; a processing circuit for processing data related to machining of the workpiece by said machining tool; and a transmitting and receiving circuit for performing at least one of transmission and reception of a wireless signal indicating information related to machining of a workpiece by said machining tool.
 15. A tool holder attachable to a spindle of a machine tool for rotatably holding a machining tool for machining a workpiece, said tool holder comprising: an electric motor for driving said machining tool and a generator for generating electric power to drive said electric motor by the rotation of said spindle.
 16. A tool holder as set forth in claim 15 , further comprising: a tool attachment part attachable to said spindle for transmitting the rotation of said spindle to said generator; a tool holding part for rotatably holding said machining tool; a casing for holding said electric motor, said generator, said tool attachment part, and said tool holding part; a locking part for preventing rotation of said casing by engagement with a non-rotating part of said machine tool.
 17. A machine tool comprising: a machine tool body provided with a spindle,-a driving means for driving said spindle, and at least one control axis for changing a relative position between said spindle and a workpiece; a control apparatus for controlling said driving means and said control axis in accordance with a machining program; and a tool attachable to said spindle and provided with a machining tool for machining a workpiece, an electric motor for driving said machining tool, and a generator for generating electric power to drive said electric motor by the rotation of said spindle.
 18. A machine tool as set forth in claim 17 , further comprising an automatic tool changer for attaching said tool to said spindle and detaching said tool from said spindle.
 19. A machine tool as set forth in claim 17 , wherein said tool changes the rotational speed of said machining tool from the rotational speed of said spindle by a predetermined ratio determined based on pole numbers of said generator and said electric motor.
 20. A method of driving a tool attachable to a spindle of a machine tool, the tool being provided with a machining tool for machining a workpiece, an electric motor for driving said machining tool, and a generator for generating electric power to drive said electric motor by the rotation of said spindle, comprising the steps of: generating alternating current having a frequency in accordance with the rotational speed of said spindle; driving said electric motor by the generated alternating current; and controlling the rotational speed of said machining tool in accordance with the frequency of the alternating current.
 21. A tool management system comprising: a tool attachable to a spindle of a machine tool, the tool comprising: a machining tool for machining a workpiece, an electric motor for driving said machining tool, a generator for generating electric power to drive said electric motor by the rotation of said spindle, a processing circuit for processing data related to machining of the workpiece by said machining tool; a transmitting and receiving circuit for performing at least one of transmission and reception of a wireless signal indicating information related to machining of a workpiece by said machining tool; and a management apparatus for performing at least one of reception of data from said transmitting and receiving circuit and transmission of data to said receiving circuit and managing the data. 